Identification and functional study of the antimicrobial peptide, QUB- 1985, from the skin secretion of the large odorous frog, Odorrana livida
Nowadays, antimicrobial resistance is one of the most serious health threats around the world. Therefore, novel antimicrobial agents are urgently needed to alleviate the pressure on conventional antibiotics. Antimicrobial peptides (AMPs) are widely known for their potent activity towards a broad spectrum of microbes. In this thesis, an AMP named QUB-1985 was discovered in the skin secretion of the Chinese Large Odorous Frog, Odorrana livida. The results of bioactivity evaluation on this peptide demonstrated that QUB-1985 could exhibit antimicrobial activity on a Gram-negative bacterium (Escherichia coli, MIC=16 μM) and a Gram-positive bacterium (Staphylococcus aureus, MIC=64 μM) in a dose-related manner, with a significant selectivity towards the Gram-negative bacterium, and had no effect on the yeast, (Candida albicans, MIC>256 μM). Also, the haemolysis assay found that no more than 18% of red blood cells were affected at at the concentration of the highest MIC value (64 μM). The peptide had an HC10 of 30.89 μM, which indicated a remarkably low cytotoxicity. QUB-1985 also exerted anti-proliferation activity on non-small cell lung cancer cells (NCI-H838) at concentrations of 10-5 M and above, and the IC50 was 1.470×10-5 M. From the above, QUB-1985 is competent to become an antimicrobial lead compound, especially towards Gram-negative bacteria and its anti-proliferation activity may broaden its utility into basic cancer research. Also, following the same templates in molecular cloning, may obtain novel AMP classes from Odorrana frogs with potent antimicrobial effects that could widen the resource of antibiotic agents. Thesis embargoed until 31 December 2026.
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